Wireless network devices with antenna diversity are employed to reduce signal fading in wireless communication applications. These wireless network device include two or more antennas. One of the antennas is employed to transmit and receive packets at a time. Signal to noise ratio (SNR) of each antenna is measured during a preamble of a packet and the antenna is selected.
Referring now to FIG. 1, a wireless network device 10 including hardware-based antenna diversity is shown. The wireless network device 10 typically includes a host device 12 such as a laptop, personal digital assistant, desktop computer or other computing device. The host device 12 includes a wireless network interface 13. The wireless network interface 13 communicates with another wireless network device 14 having an antenna system 16. The wireless network interface 13 may include a physical layer (PHY) module 20 that provides an interface between a medium access control (MAC) module 24 and a wireless medium. A host interface module 26 may provide an interface between the MAC module 24 and the host device 12. A hardware-based antenna diversity module 28 selects between a first antenna A1 and a second antenna A2 based on measurements made when packets are received.
Referring now to FIG. 2, the wireless network device 14 exchanges packets 50 with the wireless network interface 13. The packets 50 may include a preamble portion 54, a header portion 56, a variable length user data portion 58 and an error checking portion 60. The hardware-based antenna diversity module 28 samples a SNR of the preamble portion 54 and selects one of the antennas A1 or A2. More particularly, the hardware-based antenna diversity module 28 samples SNR of the first antenna during a first half of the preamble portion 54 of the packet 50. During a second half of the preamble portion 54, the hardware-based antenna diversity module 28 samples SNR of the second antenna. Based on the SNR sampling, the hardware-based antenna diversity module selects one of the antennas to be used for the packet.